1. Field of the Invention
The present invention relates to an optical disc identification apparatus and a method of identifying an optical disc. More particularly, the present invention relates to an apparatus of identifying an optical disc with use of a sectional width value of an S-curve of a focus error (FE) signal and a method thereof.
2. Description of Related Art
As disc storage technology advances, more types of discs are available, and data storage capacity of the discs is increasing as well. However, given that an apparatus for reading the data in the discs is not compatible with various kinds of the discs, the user inevitably has to purchase different disc readers, leading to unnecessary costs and superfluous consumption of resources on earth. Hence, a great number of the disc readers are equipped with an optical disc identification apparatus, such that the discs in various kinds can be read merely by a single disc reader.
Conventionally, in an apparatus of identifying an optical disc and a method thereof, the optical disc is identified based on a thickness of the disc. Please refer to FIGS. 1 and 2. FIG. 1 illustrates an embodiment of a conventional optical disc identification apparatus. FIG. 2 depicts a waveform of a RFSUM signal adopted in a conventional optical disc identification apparatus. The conventional optical disc identification apparatus includes an optic pickup unit 10, a control unit 11 and a motor driver 12. The control unit 11 is coupled to the optic pickup unit 10 and the motor driver 12 which is coupled to the optic pickup unit 10. The optic pickup unit 10 has a plurality of laser sources for emitting any of lasers to an optical disc 13 and detecting the laser reflected by the optical disc 13 to transduce the reflected laser to a detection signal det_sig. The control unit 11 controls the optic pickup unit 10 to activate any of the laser sources. In addition, under the control of the control unit 11, the motor driver 12 drives the optic pickup unit 10, so as to move an object lens 102 of the optic pickup unit 10. As the optic pickup unit 10 moves, the control unit 11 calculates the RFSUM signal based on the detection signal det_sig. Here, a peak value A1 of the RFSUM signal is generated by the laser reflected by a superficial layer of the optical disc 13, while a peak value A2 of the RFSUM signal is obtained by the laser reflected from a data layer of the optical disc 13. The control unit 11 calculates a time difference T2-T1 (referring to FIG. 2) between the peak values A1 and A2 and estimates a thickness of the optical disc 13 based on the time difference T2-T1, so as to identify the optical disc 13.
Please refer to FIGS. 1 and 2 again. The optic pickup unit 10 includes a compact disc (CD) laser source 100A, a digital video disc (DVD) laser source 100B, a focus actuator 101, the object lens 102, a beam splitter 103, and a photo detector 104. The control unit 11 includes a digital signal processing unit 110, a microprocessor 111 and a disc thickness calculating unit 112. Here, the focus actuator 101 is coupled to the motor driver 12. The CD laser source 100A and the DVD laser source 100B are controlled by the control unit 11. As the CD laser source 100A (or the DVD laser source 100B) is activated by the control unit 11, the activated CD laser source 100A (or the activated DVD laser source 100B) emits a CD laser (or a DVD laser). The focus actuator 101 receives a focus driving voltage signal of the motor driver 12, so as to achieve a uniform movement of the object lens 102. When the object lens 102 moves, the CD laser (or the DVD laser) emitted by the CD laser source 100A (or the DVD laser source 100B) is focused on the superficial layer and the data layer of the optical disc 13. The object lens 102 collects the emitted laser from the CD laser source 100A (or the DVD laser source 100B) and the CD laser (or the DVD laser) reflected by the optical disc 13. The beam splitter 103 separates the CD laser (or the DVD laser) emitted by the CD laser source 100A (or the DVD laser source 100B) from the CD laser (or the DVD laser) reflected by the optical disc 13. Additionally, the beam splitter 103 transmits the CD laser (or the DVD laser) emitted by the CD laser source 100A (or the DVD laser source 100B) to the object lens 102 and transmits the CD laser (or the DVD laser) reflected by the optical disc 13 to the photo detector 104. The photo detector 104 detects the CD laser (or the DVD laser) reflected from the optical disc 13 and transduces the same to the detection signal det_sig. The digital signal processing unit 110 calculates the RFSUM signal based on the detection signal det_sig. The disc thickness calculating unit 112 calculates the time difference T2-T1 of the peak values A1 and A2 of the RFSUM signal and estimates the thickness of the optical disc 13 based on the time difference T2-T1, so as to identify the optical disc 13. The microprocessor 111 controls the optic pickup unit 10 to activate the laser source 100A or 100B.
The conventional optical disc identification apparatus is apt to be affected by variance of the optical disc 13 or by fabrications of the motor driver 101 and the focus actuator 12 under different variables, leading to errors of the time difference T2-T1. As the errors of the time difference T2-T1 occur, the result of identifying the optical disc 13 may be wrong. Moreover, the superficial layer of the optical disc 13 has a relatively low reflectivity, such that the optic pickup unit 10 may not be able to identify a position of the superficial layer of the optical disc 13.
To rectify the drawback of the conventional apparatus and method of identifying the optical disc by the thickness thereof, a Taiwanese patent numbered I257605 provides an apparatus of discriminating the optical disc and a method thereof by characteristics of wavelengths. The operating principles of the apparatus and the method lie in that the laser sources with different wavelengths may result in dissimilar reflectivity of the discs having pits in different depths, and thereby the optical discs can be identified. Nevertheless, according to the method, the lasers emitted by the laser sources have to be focused on the optical discs for identifying the same, which may bring about excessive processing time consumed on reading the optical discs.
Taiwanese patent numbered 397969 discloses another apparatus and method of identifying an optical disc by a thickness thereof. However, inconsistent optical deviation angles may lead to inaccurate identification of the optical disc. In addition, Taiwanese patent numbered I227867 teaches still another apparatus and method of identifying an optical disc with use of a specific pickup head. Since the specified pickup head has to be employed in said invention, and an influence of noises may be easily imposed thereon, it is likely to mistakenly discriminate the optical disc. Further, Taiwanese patent numbered I260000 provides yet still another apparatus and method of identifying an optical disc based on reflectivity of the optical disc and a thickness thereof. In this method, the drawbacks of identifying the optical disc according to reflectivity of the optical disc and the thickness thereof still exist, for the optical disc may be wrongly identified due to variance of the optical disc.
In U.S. publication numbered 20050068873, an apparatus of discriminating an optical disc depending upon different thicknesses of the optical disc and a method therefor are provided. By comparing peak-to-peak values generated by different lasers, the optical disc can be identified. Nevertheless, with insensitive reflectivity arisen from variance of the optical disc, the optical disc is apt to be erroneously identified.
In U.S. Pat. No. 5,986,985, an apparatus of discriminating an optical disc depending upon reflectivity of the optical disc and a method therefor are provided. According to the invention, peak values of FE signals generated by different lasers are compared with predetermined threshold values, so as to identify the optical disc. Alternatively, a ratio of the peak values generated by the different lasers can also be compared to identify the optical disc. Unfortunately, due to insensitive reflectivity arisen from variance of the optical disc, it is also likely to inaccurately identify the optical disc according to the invention.
In U.S. publication numbered 20030039189, an apparatus of identifying an optical disc depending upon different reflectivity of the optical disc and a method therefor are further provided. According to the present invention, the optical disc is discriminated merely by comparing a peak value of an FE signal generated by a CD laser with a predetermined reference value. However, due to insensitive reflectivity arisen from variance of the optical disc, it is even more likely to inaccurately identify the optical disc according to the invention.
Based on the above, in the conventional apparatus and method of identifying the optical disc, the optical disc can be either discriminated by its thickness or identified because it is reflectivity-sensitive to specific light wavelengths. However, by applying the aforesaid method, the optical disc may be erroneously identified due to different reflectivity of the optical disc or the fabrications of the motor driver and the focus actuator under different variables.
Thus, a number of manufacturers of the optical disc identification apparatuses endeavor to overcome said issues.